An effective oral composition can maintain and preserve tooth appearance by removing dental stains and polishing the teeth. It may clean and remove external debris as well, which can aid the prevention of tooth decay and promote gingival health.
Abrasives in oral compositions aid in the removal of the tightly adherent pellicle film to which dental stains affix. Pellicle film usually comprises a thin acellular, glycoprotein-mucoprotein coating, which adheres to the enamel within minutes after teeth are cleaned. The presence of various food pigments lodged within the film accounts for most instances of teeth discoloration. An abrasive may remove the pellicle film with minimal abrasive damage to oral tissue, such as the dentin and enamel.
In addition to cleaning, it may be desirable for abrasive systems to provide polishing of tooth surfaces, as polished surfaces may be more resistant to ectopic deposition of undesirable components. Tooth appearance may be improved by imparting a polished character to the teeth, because the surface roughness, that is, its polish, affects light reflectance and scattering, which integrally relate to the teeth's visual appearance. The surface roughness also affects tooth feel. For example, polished teeth have a clean, smooth, and slick feel.
Numerous dentifrice compositions use precipitated silicas as abrasives. Precipitated silicas are noted and described in U.S. Pat. No. 4,340,583, Jul. 20, 1982, to Wason, EP Patent 535,943A1, Apr. 7, 1993, to McKeown et al., PCT Application WO 92/02454, Feb. 20, 1992 to McKeown et al., U.S. Pat. No. 5,603,920, Feb. 18, 1997, and U.S. Pat. No. 5,716,601, Feb. 10, 1998, both to Rice, and U.S. Pat. No. 6,740,311, May 25, 2004 to White et al.
The optimal degree of abrasion required to clean tooth surfaces (while not removing tooth structure) is difficult to calculate. An effective abrasive cleans and polishes the teeth with little or no damage to the tooth surface, and provides a high polish that can prevent or delay the reaccumulation of stains and deposits. Generally, the larger the particle size of a particular material, the better it will clean. But particle size, along with material hardness, affects abrasivity. So to maximize cleaning, while limiting abrasivity, a harder material is often desired. Also a factor is how often cleaning is done. For cleaning that is done less frequently than daily, a more abrasive but better cleaning oral composition may be used. Therefore, a hard material of a large particle size may provide excellent cleaning, and because it may be used less frequently than daily, its abrasiveness can still be acceptable.
Fused silica, which is harder than most known oral care abrasives, may deliver this benefit. Therefore, the present invention relates to oral care compositions comprising a fused silica abrasive, wherein the fused silica has a median particle size of at least about 10 microns and wherein the composition has a PCR of at least about 100.